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Optimized distortion correction technique for echo planar imaging
Author(s) -
Chen Nankuei,
Wyrwicz Alice M.
Publication year - 2001
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/1522-2594(200103)45:3<525::aid-mrm1070>3.0.co;2-s
Subject(s) - distortion (music) , waveform , phase (matter) , pulse sequence , eddy current , echo planar imaging , computer science , algorithm , phase distortion , physics , sequence (biology) , echo (communications protocol) , nuclear magnetic resonance , magnetic resonance imaging , chemistry , telecommunications , bandwidth (computing) , radar , medicine , amplifier , biochemistry , computer network , quantum mechanics , radiology
A new phase‐shifted EPI pulse sequence is described that encodes EPI phase errors due to all off‐resonance factors, including B o field inhomogeneity, eddy current effects, and gradient waveform imperfections. Combined with the previously proposed multichannel modulation postprocessing algorithm (Chen and Wyrwicz, MRM 1999;41:1206–1213), the encoded phase error information can be used to effectively remove geometric distortions in subsequent EPI scans. The proposed EPI distortion correction technique has been shown to be effective in removing distortions due to gradient waveform imperfections and phase gradient‐induced eddy current effects. In addition, this new method retains advantages of the earlier method, such as simultaneous correction of different off‐resonance factors without use of a complicated phase unwrapping procedure. The effectiveness of this technique is illustrated with EPI studies on phantoms and animal subjects. Implementation to different versions of EPI sequences is also described. Magn Reson Med 45:525–528, 2001. © 2001 Wiley‐Liss, Inc.